NO. 3 DUNKLE : PLANT ECOLOGY, CHANNEL ISLANDS 277 



There are but four closed communities on Santa Barbara Island, 

 two with native dominants; the Coreopsis and the Lycium-Suaeda; 

 and two exotic dominants: the Hordeum-Avena and the Mesembry- 

 anthemum. It is interesting to note that the two native associations each 

 appear to have a bird in such close association as to form a biome: the 

 Lycium-Suaeda-Larus biome on both the eastern and western terraces; 

 and the Coreopsis-Melospiza biome on the lower part of the eastern 

 terrace. 



Since Santa Barbara is essentially an elevated mesa outlined by 

 precipitous cliffs and steep bluffs it may logically and coveniently be 

 divided into two main areas. These two areas, which differ strikingly 

 in respect to evaporation rates, plant life, and soil, are: (1) mesa and 

 ridges; the central region of terraces, shallow canyons, and most of the 

 central ridge; (2) sea bluffs; the surrounding series of cliffs, benches, 

 and headlands that break off abruptly to the sea, and the upper, wind- 

 exposed parts of the western slope of the central ridge. 



Mesa and Ridge. The mesa and ridge are occupied by several com- 

 munities comparable with somewhat similar ones on the other islands. 

 These communities include a grassland, Mesembryanthemufn colonies, 

 the suffrutescent Lycium-Suaeda association, and the Coreopsis associa- 

 tion which is related to, but wholly different from, the coastal sagebrush 

 association. 



Grassland. A grassland disclimax occupies the upper part of the 

 eastern terrace, much of the central ridge, and a narrow belt extending 

 around most of the main western terrace. Much of the grassland now 

 occupies areas which were burned over and subsequently placed under 

 cultivation. The dominant plant is Hordeum murinum except for one 

 rather extensive area about the head of the landing cove where Avena 

 fatua is dominant. Even in this last locality the Hordeum is a sub- 

 dominant, while Avena occurs here and there the entire length of the 

 eastern terrace. These grasses die early in the spring, regardless of the 

 amount of moisture in the soil, and form a deep, tangled mat which 

 persists for the remainder of the dry season. 



Scattered plants and small colonies of Coreopsis gigantea, Lycium 

 californicum, and Suaeda californica pubescens occur in various parts 

 of the grassland. Plants such as A triplex semibaccata, Chenopodium 

 californicum, and Brodiaea capitata occur here and there, while small 

 plants such as Malva parviflora, Trifolium microdon, and Amsinckia 

 intermedia form an understory in many places. Amblyopappus pusillus, 

 Spergularia macrotheca, Erodiu?n cicutarium, and Mesembryanthemum 

 nodifiorum may be found in disturbed places, as along trails. 



